Desmia pentodontalis is a moth in the Crambidae family. It is found in Ecuador. The wingspan is about 34 mm. The forewings are black-brown with a cupreous tinge and with a hyaline spot in the cell, as well as a lunulate spot in the end of the cell and a lunulate spot below the cell with a whitish mark below it. There is a hyaline postmedial band. There is irregular medial hyaline band on the hindwings, as well as an irregular postmedial line.